GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: SpiralGroove on October 02, 2021, 08:33:45 PM
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Hey Bob,
Do you believe this steel collar has much chance of reducing the harmonics of my RAW barrell?
The split collar weighs 6.3 oz and can be clamped on pretty tight - it's not gonna move. Adjusting is very Crude - loosening 5 mm cap screw and sliding to different locations.
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Yep, I think that will work.... You may find that finding the correct position may be easy.... or you may find that adjustment is critical and a matter of a few thou may make a difference.... I have heard of both situations....
Bob
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Yep, I think that will work.... You may find that finding the correct position may be easy.... or you may find that adjustment is critical and a matter of a few thou may make a difference.... I have heard of both situations....
Bob
Thanks for replying🙂.
Roughly, how much weight becomes too much?
Kirk
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No idea.... However a quick check of .22LR tuners shows 4.75 to 8 oz.... Knifemakers shot filled tuners ran 4-8 oz. of shot.... and up to 14+ oz. total weight....
https://www.gatewaytoairguns.org/GTA/index.php?topic=157680.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=157680.0)
My tuners had 5 oz. movable with a total of 7 oz....
Bob
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What is the theory on tuners? Middle of barrel, out on the end, etc.?
I can see where out on the end will change the inertia of the end of the barrel and hopefully let the projectile pass before moving. But not sure if this is the theory behind how they work.
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Most adjustable (threaded) tuners are mounted at, or beyond, the muzzle.... By fine adjustments you can vary the position of the muzzle when the projectile exits from it.... This can provide a dramatic reduction in vertical stringing at one range, which is why it is used by benchrest rimfire competitors.... It can also be used to get a "node" at the muzzle, where barrel movement is at a minimum.... Having the weight at the muzzle also reduces the frequency and amplitude of the vibration there....
The other alternative is a sliding weight that you move along the barrel to adjust the harmonics.... I think they are mainly used to get a "node" (where the movement is minimal) to occur at the muzzle....
Bob
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FYI: I bought some rubber Limbsaver barrel vibration dampeners. They call them 'Sharpshooter X-Ring Barrel Deresonator'. I haven't experimented with them much yet. The directions say slide them on supported barrels 3/4" from the stock and on floating barrels 3/4" from the muzzle.
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Guys,
FWIW
I just installed another MAD device on my Varmint 22 cal, that I have been testing with resized pellets etc.
The before group straight out of the can shot into a shotgun group of 3-1/2" x 1-1/2",
@ 50yds = 900+ fps, using stock Crosman OEM pellets 14.3grs
The best group for .2170" head sized OEM Crosman pellets = 5.300" x 2.25", same 50 yds,
nothing changed from the above rifle settings.
Installed a Mercury fill shotgun chamber MAD devise,
and reshot from the same OEM Crosman tin, and recorded a 2.030" x .500" at the above yardage.
Resized .2170" head pellets from the same can, landed in a group that was .930" x .600",
all groups were measured outside edge to outside edge.
This Mercury filled MAD devise is pictured here on pg#19 and post #372,
https://www.gatewaytoairguns.org/GTA/index.php?topic=157680.360 (https://www.gatewaytoairguns.org/GTA/index.php?topic=157680.360)
I installed it right behind the LCD on the barrel.
This is the third time, I have tried and install this device, on 3 different type of 22 cal PcP rifles,
and I have seen great improvements in the total overall group size,
with reduced scattered pellets, and cleaner rounder group sizes,
I'll be testing further all head resized pellets to compare against the first series shot,
to see the final results.
Tia,
Don